Composite image sequence only using one image in the sequence
EDIT: The settings in the Image Sequence node are a bit different then I epxlained before - my answer only worked because I tested it with an image sequence starting at frame #1 - while yours beings with #884. So here's how it all works together:
Your mistake is, you have set an Offset of 883 in the Image Sequence node and set your animation to render from frame 884 to 1271 (my month and year of birth :D ), while at the same time you have set Start Frame set to 1 in the Image Sequence node - but your animation starts at frame 884.
What the three values Frames, Start Frame and Offset do is the following:

Frames tells Blender how many images are in that sequence
Start Frame tells Blender on which frame the sequence should begin to run
Offset tells Blender what to add to 1, to get the image number on the specified Start Frame

So, in order to make this work you must either render the animation from frame 884 to 1271 and make Blender believe you have 1271 images starting at frame 1, set
Frames = 1271, Start Frame = 1, Offset = 0
in the Image Sequence node. This will render on each frame the image with the same number as the frame. So image#0001 on frame  1, image#0002 on frame 2 etc. Since your image sequence starts at #0884, the frames 1-883 will stay empty and the frames will start getting rendered at frame 884. If you would have set Frames to 388, then Blender will stay at image#0388 until the end of the animation which is not what you want (because there is no image#0388).
Or the better and more correct way would be, you render your animation from 884 to 1271 and set the following values in the Image Sequence node:
Frames = 388, Start Frame = 884, Offset = 883.
This way you can set the actual number of images your sequence has, and Start Frame tells Blender on which frame you want to render the first image of your sequence. Since the first image is usually #0001, you have to enter the Offset to tell Blender you don't want to begin with image #0001, but with 1+883 i.e. image#0884.
Whatever the range of your animation might be, let's say you want an animation starting at frame 1 and ending at frame 3000 - that's not really relevant for the Image Sequence node. You can render frames 1-3000, and if you want your image sequence to begin at frame 100, then set Start Frame = 100. Blender assumes you want image#0001 on frame 100, so you need the Offset = 883 to correct that.